Insulated Glass Units (IGUs), also known as double glazing units, are generally formed from two spaced apart panes of glass separated by a peripheral spacing frame. The frame and glass forms a hermetically sealed chamber so as to provide a transparent insulating barrier. However, the peripheral frames are bulky, expensive and unsightly, and interfere with the view through the glass panels, especially when an IGU glass wall is formed by abutting several IGUs together in an edge to edge manner.
Other arrangements use point fixing structures which have a spacer between the glass panels to mount the IGUs. Point fixing devices allow the use of much slimmer peripheral frames.
One particular known point fixing structure is disclosed in JP 2000104456 A. This structure includes a spacer, for providing an air gap, between an inner and an outer glass panel, the spacer being arranged such that inner faces of the inner glass panel and the outer glass panel directly abut the respective faces of the spacer. This structure further includes a cylindrical collar assembly comprising several parts inserted central to the spacer. In this configuration, a void is formed between an inner radial surface of the spacer and an outer radial surface of the collar assembly.
To seal the air gap from the external environment, a sealant is disposed within the void and a bolt is inserted central to the collar assembly. An oversized nut is then engaged to a threaded end of the bolt and tightened such that the inner and outer glass panels are clamped against the spacer. During clamping, the sealant is squeezed into and retained in the void by the inner surface of the over sized nut, and the collar assembly serves to prevent over tightening.
A disadvantage with this type of point fixing structure is that the collar comprises a stacked arrangement of multiple parts with different compression characteristics and variable dimensions. Accordingly, it is difficult to ensure the height of the overall collar assembly is reliably within tolerances required to provide accurate compression when tightening the nut. For example, when the glass panels are clamped against the spacer, the components of the collar assembly, such as the sealant and sealing washers are squeezed by differing degrees. Furthermore, as multiple parts of the collar assembly may need to be inserted by hand, it is difficult to automate the manufacturing process of an IGU.
Another disadvantage of this type of point fixing structure is that it may be difficult to assemble an IGU unit when the glass panels are in a vertical orientation, which is advantageous in an assembly line. For example, the main sealant of JP 2000104456 A would likely not be held in place during manufacture between the inner radial surface of the spacer and an outer radial surface of the collar assembly, if the glass unit was constructed in a vertical orientation.
Yet another disadvantage of this type of point fixing structure is that the spacer serves only to hold the glass panels in spaced relation. The spacer does not directly retain any sealant which can be used as a seal to retain air in the air gap, and also ensure unified fit with the glass panels which may have surfaces that are not entirely congruent with the respective faces of the spacer.
The present invention seeks to ameliorate one or more of the above-mentioned disadvantages.